Method of eliminating carbon dioxid and oxygen in electric smelting-furnaces.



J. THOMSON.

METHOD OF ELIMINATING CARBON DIOXlD AND OXYGEN IN ELECTRIC SMELTINGFURNACES.

APPLICATION mgo OCT. 24. 1918.

1,308,879 PatentedJuly 8,1919.-

% luvs/lion UNITED sTA Es PATENT OFFICE.

JOEIN THOMSON, OF YORK, N. Y.

IETHOD OF ELIXINATING CARBON DIOXID AND OXYGEN IR ELECTRIC SMELTING-FURNACES.

Specification of Letters Patent.

Patented July 8, 1919.

Application fl1ed ctohcr 24, 1918. Serial No. 259,560.

To all whom it may concern: Be it known that I, J our: THOMSON, a c1t1'zen of the United States, and a resident of the borough of Manhattan,city of New York, county and State of New York, have invented certainnew and useful Improvements in Methods of Eliminating Carbon Dioxid andOxygen in Electric Smelting- Furnaces, ofwhich the following is aspecification, reference being made to the accompanying drawing, forminga part thereof.

This invention relates to metallurgy and concentrates thereof.

The single figure of the drawing is a sectional view of a' furnace aswhen fully charged, and is.a semi-diagrammatic illusof power, as E.

tration'which is employed to show a preferred manner of carrying themethod into useful effect rather than to denote precise details ofconstruction, v

The type of electric furnace required to utilize this method is one inwhich a carbon thermal element-such as a resistoror an arc-imparts itsheat by radiation to an underlying charge. 4

In essence, th furnace, as here depicted, is comprised in-a brickcasing, A, having a chamber, B, with a zig-zag resistor, C, interpolatedbetween and suspended by suitable terminals, as D, D, energized from asource If, for example, the furnace is to be used for smelting roastedzinc concentrates, according to the classical formula ZnO+C= Zn-l-CO',the zinc being distilled in the form of fume, then the resistor-chamberwould needs be provided with a throat, as F, leading to a suitable meansfor condensation, not deemed necessary of being here illus trated. So,too, an open retort. H, disposed beneath the resistor, would benecessary, which contains the charge; and this retort, when exhausted,is preferably capable of being removed and substituted by a duplicaterecharged member.

One of the gravest difficulties metwith in zinc-smelting is theprescnce'of G0,; which has the pernicious effect of forming ZnO, orblue-powder, or a combination of both, and to the extent thereof,whatever it may be, minimizing the quantity of zinc that may becondensed in the form of liquid metal. Another grave diflicultyresulting from the presence of CO in electric furnaces is its attack onsuch portions thereof as may best be made from amorphous or graphitlzedcarbon.

The foregoing controlling objections are obviated by the practice" ofthis method; which consists in placing upon the top of the charge,preferably prior to its insertion in the furnace, a distinct andrelatively thin layer of broken or granular carbon and maintaining it ata temperature of about or above l,l00 C.

In view of the state of the art, it may seem like asuperero ativestatement that the use of carbon for t e elimination of CO in thepresence of zinc-fume has hitherto been proposed; but in such instances,or as have been shown in patents issued to others as well as the presentapplicant, the carbon has been employed as a curtain or porous septumin, or at, or near to, the condenser.

It should be borne in mind that in dealing with zinc-fume and the gasesof carbon the following reversible reaction takes place:

CO C2200 (1) At the smelting temperature, the reaction is from left toright, that is in the presence of carbon any G0, which maybe Theconsequence is that it is nearly always difiicult if not impracticableto maintain carbon at such a temperature, when in or contiguous to thecondenser, as will be ado quate to produce the desired result. In factit has variously been proposed to separately heat such carbon-screensgwhich, while effective as to the elimination of the pernicious gas, hasthe contingent objectionable result of super-heating the zinc-fumeimmediately prior to its entry into the condenser.

Moreover, CD, is generated at. a much lower temperature than CO, or atthe latters initial temperature of active reaction with ZnO, whereforethe furnace chamber andthe condenser becoine more or less pre-filledwith an oxidizing atmosphere.

sarily be adhered to; as, for he stokeddn, through 0 nings mice-walls,or be sifted-1n throng tubes or These ditiiculties and objections arewholly obviated, in a practical sense, by the-simple expedient ofapplying directly upon the top of the charge S a relatively thin layerof granular carbon R. This top dressing of carbon is virtually afilter-bed, through which all of the ascending volatiliz ed fume, vaporor gases generated in and ascending from the charge must percolate.

When feasible to do so,'the filter-carbon should preferably be'pre-heated; consequently, when the charged retort is placed in thefurnace, the resistor, orwhatever su'bstitute therefor may be used,quickly raises the temperature of this carbon to a state of incipientincandeseence both before CO is And the same observations apply to suchoxygen as may be entrained or combined in the charge. Then, as theZinc-fume mingles only with perfectly clean CO, the gases -may beprogressively cooled as they flow toward the condenser wherea-t all ofthe zinc can be condensedto liquid metal. Moreover, in thesecircumstanceasuch portions of the furnace asmay best be constructed ofcarboniferous materials are completelyimmune from destructive attack andwill endure indefinitely;

It is true-that, when the reaction begins, a certain minimum amount ofthe'filtercarbon, in direct contact with the charge, is lost byreduction; but this consumption ceases when a thin interposed layer ofresiduum is produced and the only further diminution will'be that due tothe reaction with up-flowing C0,, or O, or hydrous vapors.

Nor does the addition of this filter-carbon involve extra expense; forit thus becomes feasible to at least correspondingly;diminish the amountof reaction-carbon mixed with the concentrate. .Or, to otherwise statethe case, instead of having an excess of carbon mixed with the Zn().serving to in.- crcasc the production of C0,, it is placed upon the topof the charge where it acts to convert the pernicious gas into one thatis benign.

hile the within described mode of applying the filter-carbon to an orecharge is regarded as preferable, such need not necesexample, it may thefur the said thermal element from the erosive attack of CO and O', oreither of them, which consists ih covering the said charge with a layerof filter-carbon and maintaining it. at a temperature of about or aboveeleven hundred degrees centigrade.

2. In an electric-smelting furnace provided with a carbon thermalelement whose heat is transmitted by radiation to an underlying reactingcharge composed of. ZI10+C, the method of converting, at the source ofgeneration, CO into G0 which consists in covering the said charge with alayer of filtor-carbon and maintaining it at a temperature of about orabove eleven hundred degrees. centigrade.

3. In an electric smelting furnace provided with a carbon thermalelement Whose heat is transmitted by radiation to an underlying chargein which CO and O, or either of them, maybe evolved and whose presencewould be pernicious, the method of converting them into benign gaseswhich consists in covering the charge with a layer of filter-carbon andmaintaining it at a temperature of about or above eleven hundred degreescentigrade.

4. In an electric smelting furnace provided with a carbon thermalelement whose heat is transmitted by radiation to an under: lying chargein which CO and O, or either of them, may be evolved with perniciouseffect, the method of rendering the said gases non-oxidizable whichconsists in applying to the top of the charge, prior to its introductionin the furnace, a layer of filter-can bon which is thereafter acted uponby the thermal element and maintained at a temperature higher than thecharge. 5. In the treating of metals in a furnace having an electricalthermal element, the method which comprises employing the thermalelement to heat the metal sufliciently to' drive off fame of the metaland protecting the thermal element a ainst the action of gases such asCO or g, passing off or mixed with the fume, by filter carbon lo catedbetween the metal being treated and the thermal element.

6. In the treating of metal in an electric furnace having a thennalelement compris ing cmlmn as an essential part than f. the methml whichcmnprl: .a: employing the the"- 111211 element. to heat a char e of the.metal sufficiently to drive off met-:11 fume and pro tecting the thermalclement, against, the #0- tion of ()0 or O by 1L layer of filter-carbonwhich is on said charge, said layer of filtercarbon being located sothat the heat suppliekl l'rmn (ilk: thermal OlfiilK'nl', in the metal 10to he uon eriml said layer.

This specification signed and witnessed this 13th day ml September, A.D. 1 318.

J (JHN THOMSON. Signal in tin; }')lO5unCQ 0f RALPH M. THOMSON, H.. (I).\VEED.

Erin) funm mint pass through

